This invention is directed to status monitoring and more particularly to the operational status monitoring of the BLC system of an aircraft.
Short takeoff and landing (STOL) airplane, utilizing boundary layer control (BLC) for high lift, directly depend on BLC system performance for stall margin and lateral controllability. This dependency demands that the system have adequate failure detection and warning devices, and a reliable BLC status monitoring system for personnel and airplane safety. The former, is necessary for airplane primary structure protection since, BLC systems are generally designed to operate on direct engine bleed, with associated high pressures and temperatures, due to installation space limitations. The latter is essential to meet the basic BLC system design condition dictated by engine-out performance requirements, namely, the maintaining of adequate stall margin while still achieving acceptable climb gradient for go-around or acceptable descent angle for landing after an engine failure. To meet this latter condition, it is imperative that BLC system status be continuously monitored and the crew be warned of system malfunction prior to aircraft high-lift performance deterioration.
Past attempts to detect failures and monitor the operation status of BLC systems have been based on deductive logic, i.e., system status was deduced from the position of control valves and high lift surfaces. The basic assumption made was as follows: if the valves and high lift surfaces are in the required position during the time all engines are operating, the system has no failures and maintains the capability to deliver design blowing momentum, in the designed distribution pattern, in the event of an engine failure. This simple approach does not provide the positive indication of capability required by flight safety considerations because it does not provide a check for ducting or nozzle failures such as rupture or blockage due to component failure, material fatigue or hostile action. These failures if undetected can cause: (a) a significant reduction in low speed maneuver capability and operational safety margins, in the event of an engine failure, due to loss of blowing momentum and/or distortion of momentum distribution (premature "stall" of some lifting surfaces); (b) a loss of engine thrust and possibly engine damage due to extraction of engine bleed beyond allowable engine bleed limits; and/or (c) damage to airplane primary structure, control cables, sense lines, electrical wiring and other vital equipment, in close proximity to the ducting, by exposure to high temperature air.
It is an object of this invention to provide a new and improved status monitoring apparatus for boundary layer control systems.
It is a further object of this invention to provide a BLC system status monitoring apparatus that monitors the operation of the air delivery and momentum injection subsystems of the BLC system.
It is a still further object of this invention to provide a BLC system status monitoring apparatus adapted to detect a rupture or blockage of the air delivery and momentum injection subsystems of the BLC system.